Redistribution of organosilanes



United States Patent Ofi .lce

3,135,778 Patented June 2, 1964 3,135,778 REDISTRIBUTION F ORGANOSRANES Geoffrey John Sieddon, West Kilbride, Scotland, assignor to imperial Chemical Industries Limited, London, England, a corporation of Great Britain No Drawing. Filed Sept. 27, 1961, Ser. No. 140,995

laims priority, application Great Britain Oct. 28, 1960 12 Claims. (Cl. 260-4482) This invention relates to the production of organosilicon compounds and more particularly to the production of organohalogenosilanes.

Organosilicon compounds such as the organosilanes and organohalogenosilanes are well known and widely available and may be prepared in a variety of ways. Frequently, however, the method of preparation does not give as end products the most desirable products for use in further processing. It is therefore necessary in many cases either to discard a considerable proportion of the products or to effect a redistribution reaction among the end products in order to increase the yields of the desired organosilanes and organohalogenosilanes. This redistribution step has been achieved by sundry methods, for example, by reaction under pressure at elevated temperatures in the presence of aluminum chloride as catalyst. The methods hitherto available however suffer from one or more disadvantages. Thus, for example, the aluminum chloride catalyzed reaction suffers from the disadvantage that temperatures in excess of 280 C. are required to ensure an adequate rate of reaction. Redistribution using aluminum chloride as a catalyst in presence of a silane containing silicon-bonded hydrogen atoms has also been widely used. This process however suffers from two disadvantages. A long reaction time is required to get adequate redistribution and it is adversely afiected by the presence of hydrogen chloride in the reaction mixture which it is difficult to avoid.

An object of the present invention is to provide a process for the redistribution of organosilanes. Another object is to provide such a process which can be carried out more rapidly than hitherto. A further object is to provide such a process which is less affected by the presence of hydrochloric acid in the reaction mixture than have been previous processes. Other objects will appear two other silicon compounds. It is however preferred to use amounts within the range 4 to 8 percent.

The amounts of aluminum chloride used may vary widely, for example, from 2 to 10 percent by weight of the two first mentioned silicon compounds. It is in general, however, preferred to use amounts of the order of 4 to 8 percent by Weight.

The amount of magnesium metal used may vary from about 1 to about 10 percent by weight of the reaction mixture. Amounts of the order of about 3 to 5 percent are in general preferred and normally gives satisfactory results.

The reaction may be carried out over a wide range of elevated temperatures for example, up to about 400 C. It is normally preferred, however, to operate at temperatures within the range ISO-200 C.

The reaction is normally preferably carried out at superatmospheric pressures which may, if desired, be generated autogenously. The pressure may be up to the order of 200 atmospheres. Pressures of the order of 10 to 15 atmospheres are in general satisfactory and are preferred.

The proportions of the two reactant silicon compounds used may vary widely. It is however preferred to employ them in such proportions that there are between 0.3 and 3 chlorine atoms per silicon-bonded organic radical in the reaction mixture. In many cases it is further preferred to use a reaction mixture which contains equimolecular proportions of chlorine and silicon-bonded organic radicals.

Our invention is further illustrated by the following examples in which all parts and percentages are by Weight.

Examples 1 to 3 10.8 parts of trimethylchlorsilane and 14.9 parts of methyltrichlorsilane together with 2.5 parts of methyldichlorsilane, 2.5 parts of aluminum chloride and 1 part of magnesium were heated together in a closed glass-lined reaction vessel at 150 C. for 3 hours. The reaction vessel was then cooled, opened and the liquid product decanted therefrom. This liquid product was separated into its constituent chlorsilanes by distillation.

The reaction was repeated twice. In the first repetition heating was for 8 hours and in the second repetition for 16 hours. The products obtained in each case are shown hereinafter. inthe following table.

Heating Product analysis (percent) Example period, Product,

hours parts (CHzQ SiCl (CH3)2S1C11 01138101 OHgSlHClg ACCOl'dlIlg to the present invention these ob ects are Example 4 where R" is an alkyl or aryl group and c and d are 0, l, 2 or 3 and c+d is not greater than 3. Suitable examples of such compounds are methyldichlorsilane, trichlorsilane and phenyldichlorsilane. This silane may be used in amount from 2 to 10 percent of the total weight of the 6.6 parts of tetramethylsilane, 22.3 parts of methyltrichlorsilane, 2.2 parts of methyldichlorsilane, 2 parts of aluminum chloride and 1.5 parts of magnesium were heated together in. a closed glass-lined reaction vessel at 320 C. for 35 minutes. The reaction vessel was then cooled and 31 parts of liquid reaction product removed therefrom. 82 percent of this product was dimethyldichlorsilane.

The process was repeated with the omission of the magnesium. In this case 30.5 parts of product containing 31 percent of dimethyldichlorsilane were obtained thus showing that the redistribution had taken place much more slowly in the absence of magnesium.

Example 5 The procedure of Example 1 was repeated except that 3 the mixture was heated at 155 C. for 16 hours. There was recovered from the reaction product 230 parts of dimethyldichlorsilane.

This process Was repeated with the omission of the 10 percent by weight of the two firstmentioned compounds of aluminum chloride and from 1 to about 10% by weight of the reaction mixture metallic magnesium, the reaction being carried out under a super atmospheric methyldichlorsilane. in this case the product contained 5 pressure of up t the rd r f 200 atmospheres, only 4.1 parts of drmethyldlchlorsilane. 2. A process as claimed in claim 1 wherein the amount E l 6 t0 8 of silane containing silicon-bonded hydrogen used is with- Mixtures consisting of 432 parts of trimethylchlorsilane, the range of from to @0111: 8 Per cent 596 parts of methyltrichlorsilane, 52 parts of methyldi- T A as clalfned clam 1 Wherem the 31mm chlorsflane, and 52 parts of aluminum chloride were 10 num 01110110518 used in amount from about 4 to about heated with varying proportions of metallic magnesium 8 Percgntat 150 C. for 16 hours in a stainless steel pressure P Q as claFnedmclalm 1 Wherem the amount vessel. The reaction product was separated into its conof magneslum metal frofn abPut 3 to abPut 'P Stituent chlorsflanes' The products obtained and the v 5. process as claimedln claim 1 wherein the reaction quantities f magnesium used are shown i h followi g 15 15 carried out at an elevated temperature of not more table. than about 400 C.

The process was repeated using no magnesium and 6. A process as claimed in claim 5 wherein the temthe results obtained are also shown in the table. perature of operation is within the range ISO-200 C.

Products (parts) E 1 M xamp e (pargs) I (CHa)sSiCl (CHa)2SiG12 CH3SiG1a CHsSiHOIr 31 931 42 34 10 41 898 61 1s 15 49 s43 78 2o 134 605 277 10 Example 9 7. A process as claimed in claim 1 wherein the pres- 288 parts of tetramethylsilane, 516 parts of silicon Sure used 15 0f I116 6r of 10 to 15 atmospheres, tetrachloride and 91 parts of trichlorsilane were heated A Process as clalm 1 Whemm the P together with parts f aluminum hl d and 16 parts trons of the two reactant silicon compounds are such that of magnesium in 'a steel autoclave at 160 C. 'for 17 there are from about 0.3 to about 3 chlorine atoms per h Th maximum pressure ttai d a 12 atmossllicon-bonded organic radical in the reaction mixture. pheres. At the end of the heating period the autoclave 39 9. A process as claimed in claim 8 wherein the reaction was cooled, opened and the liquid contents removed. mixture contains equiznolecular proportions of chlorine 851 parts of product were recovered from WhlCh were d Silicombonded organic radicals. Separated 710 Je 0f dlnlthyldlchlofsllne, Parts of 10. A process as claimed in claim 1 wherein the silane 1 Y 1 3 fl Parts of methylmchlorsllane and 40 containing silicon-bonded hydrogen is methyldichlorparts 0 nc ors ane. silane What I claim is: 11 A 1. A process for the redistribution of organosilanes c as claimed m clam} wilerem.the silane on aimng s1 icon-bonded hydrogen is trichlorsrlane. comprising reacting together at elevated temperatures a 12 A recess as d d l 1 h th compound of the general formula R SiCl and a differp alme m c m eriam en: Compound of the general formula Rb,sicl(4 b) containing silicon-bonded hydrogen is pnenyldichlorwhere R and R are alkyl groups, a is an integer of silane from 1 to 4, and b is an integer of not greater than 3, in the presence of from about 2 to about 10 percent by References Cited m the file of thls Patent weight thereof of a silane containing silicon-bonded hy- U ITED STATES PATENTS drogen of the general formula R "SiH ')Cl where R" is selected from the group consisting of an alkyl and an aryl group, 0 and d are integers of not greater than 3 and c-i-d is not greater than 3, from about 2 to about 2,786,861 McEntee Mar. 26, 1957 OTHER REFERENCES Fukukawa et al., 51 Chem. Abstracts 12845 (1957). 

1. A PROCESS FOR THE REDISTRIBUTION OF ORGANOSILANES COMPRISING REACTING TOGETHER AT ELEVATED TEMPERATURES A COMPOUND OF THE GENERAL FORMULA R2SICL(4-A) AND A DIFFERENT COMPOUND OF THE GENERAL FORMULA RB''SICL(4-B) WHERE R AND R'' ARE ALKYL GROUPS, A IS AN INTEGER OF FROM 1 TO 4, AND B IS AN INTEGER OF NOT GREATER THAN 3, IN THE PRESENCE OF FROM ABOUT 2 TO ABOUT 10 PERCENT BY WEIGHT THEREOF OF A SILANE CONTAINING SILICON-BONDED HYDROGEN OF THE GENERAL FORMULA RC=SIH(4-C-D))CLD, WHERE R" IS SELECTED FROM THE GROUP CONSISTING OF AN ANKYL AND AN ARYL GROUP, C AND D ARE INTEGERS OF NOT GREATER THAN 3 AND C+D IS NOT GREATER THAN 3, FROM ABOUT 2 TO ABOUT 10 PERCENT BY WEIGFHT OF THE TWO FIRST MENTIONED COMPOUNDS OF ALUMINUM CHLORIDE AND FROM 1 TO ABOUT 10% BY WEIGHT OF THE REACTION MIXTURE METALLIC MAGNESIUM, THE REACTION BEING CARRIED OUT UNDER A SUPER ATMOSPHERIC PRESSURE OF UP TO THE ORDER OF 200 ATMOSPHERES. 